The present invention relates to an improvement in the method on an industrial scale for the preparation of N-[3(3-cyanopyrazole[1,5-a]pyrimidine-7-yl)phenyl]-N-ethyl-acetamide of FORMULA I. 
This substance belongs to the group of (7-phenyl)pyrazole-[1,5-a]pyrimidines-(2-amino-disubstituted) which are useful in human medicine as anxiolytic, hypnotic-sedative, and antiepileptic agents as well as skeletal muscle relaxants.
The present invention involves a simpler method with a higher yield for obtaining the product on an industrial scale, which is the object of the present invention, starting with N-[3-[3-(dimethylamine)-oxo-2-propenyl]phenyl]acetamide (II), in xe2x80x9cone stepxe2x80x9d with a chromatographic purity of 99.5% using HPLC.
The synthesis of this compound has been the object of other patents, such as for example, U.S. Pat. No. 4,626,538 wherein the method for obtaining the product, indicated in DIAGRAM I, is applicable to many compounds of the same family and U.S. Pat. No. 5,714,607, where an improvement of the conditions and the reaction medium of the last step are described, in particular for the compound of the present invention, by the addition of water to the acetic acid, reducing reaction times and temperatures. 
The method, object of the present application, for obtaining the substance of FORMULA I, is a xe2x80x9cone stepxe2x80x9d reaction without isolation of the intermediary (III), (N-[3-[3-(dimethylamine)-1-oxo-2-propenyl]phenyl-N-ethyl-acetamide), generated by the addition in portions of N-[3-[3-(dimethylamine)-1-oxo-2-propenyl]phenyl]acetamide (II) to a suspension of ethyl iodide and sodium hydride (50-60% in mineral oil), using dimethylformamide as a solvent and at a temperature between xe2x88x9215 and 20xc2x0 C., preferably between xe2x88x9210 and 5xc2x0 C. The suspension resulting from this synthesis step is diluted with water at a temperature of 0 to 30xc2x0 C. with the dissolution of the formed compound (III) (N-[3-[3-(dimethylamine)-1-oxo-2-propenyl]phenyl-N-ethyl-acetamide), at a ratio of water/dimethylformamide (DMF) of 0.3-1.5 by volume, preferably at 0.5-0.8 by volume (SOLUTION A). 
It has been found that the addition of this SOLUTION A to SOLUTION B, which contains the 3-amino-pyrazole-4-carbonitrile (IV) (at a molar ratio of 1 to 2, preferably 1.1-1.5) dissolved in dimethylformamide/hydrochloric acid 2-3 N and (RV: 0.3 to 2.0 by volume) at 20-60xc2x0 C., preferably at a ratio of volume of DMF/hydrochloric acid 3 N of 0.4-0.7 by volume and at 25-35xc2x0 C., allows:
The titration of solution A, which contains compound III, which minimizes the possibility of decomposition of said compound by exposure to the acidic medium.
The condensation reaction and subsequent cyclization between compounds III and IV to be rapid since it is carried out at a pH lower than 3, preferably lower than 2.
Obtaining the FORMULA I compound in excellent quality and with a reaction time between 3-5 hours.
From the resulting suspension, or diluted with more water and cooled to a temperature lower than 5xc2x0 C., a slightly yellowish clear product is obtained with a chromatographic purity by HPLC not less than 99.5% and a global molar yield from both steps of at least 85%, preferably 90% to 95%. The yield obtained when applying the methods described in patents U.S. Pat. No. 4,696,538 and U.S. Pat. No. 5,714,607 are noticeably lower (a difference of approximately 10%) in comparison to the present method.
The color of the crude solids obtained decreases markedly after one recrystallization with solvents such as isopropanol, acetone, 2-butanone, ethyl acetate or methanol. During this process 5-10% by weight of carbon can optionally be used.
Using the method of the present invention, an important advantage lies in achieving a significant shortening of the preparation times by avoiding the isolation of (N-[3-[3-(dimethylamine)-1-oxo-2-propenyl]phenyl]-N-ethyl-acetamide) (III). This is obtained in a dimethylformamide medium and the isolation is complicated and tedious.
By applying the method of the present invention, the quality of this intermediate (determined by HPLC of the solutions) can be expressed as being no less than 94% in area, generally between 95-98%, which is sufficiently pure to ensure the obtainment of the N-[3(3-cyanopyrazole[1,5-a]pyrimidine-7-yl)phenyl]-N-ethyl-acetamide in very good quality.
The yields of these two synthesis steps were not published in U.S. Pat. Nos. 4,626,538 and 5,714,607. However, upon reproducing the samples described in said patents in our laboratory, we have obtained yields markedly lower than those achieved with our xe2x80x9cone stepxe2x80x9d method. These differences in yield are greater than 10% in favor of the present method.
The same were obtained upon reproducing Sample No. 6 of U.S. Pat. No. 4,696,538 in order to obtain N-[3-[3-(dimethylamino)-1-oxo-2-propenyl]phenyl]-N-ethyl-acetamide (III), and sample No. 11 of the method detailed in U.S. Pat. No. 5,714,607 for obtaining N-[3(3-cyanopyrazole[1,5-a]pyrimidine-7-yl)phenyl]-N-ethyl-acetamide (I).
These improvements (fewer number of hours during the preparation and a higher yield), added to the excellent profile of impurities determined by HPLC of the N-[3(3-cyanopyrazole[1,5-a]pyrimidine-7-yl)phenyl]-N-ethyl-acetamide obtained by way of the present method, make this the preferred method for use on an industrial scale. Moreover, the use of the present method ensures a low content of impurities with Rrt (Relative retention time by HPLC) greater than COMPOUND I. We have found that said impurities are difficult to eliminate by conventional purification methods of recrystallization.